Digital computers have evolved to include various different user interface devices that enable a user to steer a cursor around a screen to select among displayed menus and other objects and to perform various other functions. A computer mouse is one widely used type of user interface device. The mouse is usually connected by cable to the computer, but may instead be connected via a wireless interface. The mouse may use a roller ball or a light source (e.g., LED) coupled to a light sensor to sense movement of the mouse. Movement of the mouse is interpreted by the computer as, for example, a user command to move a cursor on the screen. The mouse generally includes several buttons that can be actuated by a user to, for example, signal the user's selection of a displayed menu or other object that is adjacent to the cursor.
In portable computer applications the mouse has the drawback of being separate from the computer. Accordingly, the user can be inconvenienced by the need to remember to bring along the mouse when traveling with or otherwise moving the computer, and by the need to separately pack both the computer and mouse. This inconvenience has prompted the evolution of other user interface devices that are integral to the computer, such as a touchpad disposed in the computer housing and a joystick associated with the computer keyboard.
In the above-mentioned related application, a cellular communication terminal can be configured to function as a mouse for a proximately located computer. The cellular communication terminal includes a cellular transceiver, a communication interface, an accelerometer, and a controller. The cellular transceiver is configured to communicate over a wireless cellular interface with a cellular network. The communication interface is configured to be communicatively coupled with the proximately located computer. The accelerometer is configured to generate acceleration information that is indicative of movement of the terminal. The controller is configured to communicate through the cellular transceiver with the cellular network according to a cellular communication protocol, and to selectively operate in a mouse mode during which the controller generates terminal movement information based on the acceleration information from the accelerometer and communicates the terminal movement information through the communication interface to the proximately located computer. It may also be configured to function as a mouse for the cellular communication terminal itself.
A potential drawback with this system may occur if a user brings the computer and the terminal on a means of transport which is itself accelerating relative to the earth. Then the acceleration information generated by the accelerometer is influenced by the acceleration of the means of transport and is generally not a true measure of the user's movements of the terminal relative to the computer.
An object of the present invention is to provide an arrangement providing a reference measurement of the acceleration of a reference frame in relation to which the acceleration of the terminal is to be measured.